Spark plug gap

[timh975]

Hey guys, just replaced the original platinum tip plugs on my 6.0 liter with the iridium plugs. The new plugs are pregapped at .040", but the sticker under the hood says to gap the plugs at .060". The guy at the dealer said to leave the plugs at .040", it will run fine and will also run a little cooler. So for now I left them at .040", and it runs good. Should I take them back out and set them at .060", or leave them? If I leave it will that decrease gas mileage you think?

[Bish]

Hey guys, just replaced the original platinum tip plugs on my 6.0 liter with the iridium plugs. The new plugs are pregapped at .040", but the sticker under the hood says to gap the plugs at .060". The guy at the dealer said to leave the plugs at .040", it will run fine and will also run a little cooler. So for now I left them at .040", and it runs good. Should I take them back out and set them at .060", or leave them? If I leave it will that decrease gas mileage you think?

 

<{POST_SNAPBACK}>

 

 

 

The iridiums ate .040 and everything else is .060.

[rjirvine]

Hey guys, just replaced the original platinum tip plugs on my 6.0 liter with the iridium plugs. The new plugs are pregapped at .040", but the sticker under the hood says to gap the plugs at .060". The guy at the dealer said to leave the plugs at .040", it will run fine and will also run a little cooler. So for now I left them at .040", and it runs good. Should I take them back out and set them at .060", or leave them? If I leave it will that decrease gas mileage you think?

 

<{POST_SNAPBACK}>

 

 

 

The iridiums ate .040 and everything else is .060.

 

<{POST_SNAPBACK}>

 

 

 

 

I replaced my plugs at 93k from platinums to iridiums. You're correct, the gap went from .060 to .040. I checked them before I installed them just to make sure, and they were all correct. I didn't notice any difference, and it idles smooth.

[MS3DALE]

This should help,

 

Document ID# 1396703

 

 

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Subject: Information on New Spark Plugs and Gapping #03-06-04-060 - (10/24/2003)

 

 

 

Models: 2004 Buick Ranier

 

2002-2004 Cadillac Escalade, Escalade EXT

 

2003-2004 Cadillac Escalade ESV

 

2004 Cadillac CTS-V

 

1997-2004 Chevrolet Corvette

 

1998-2002 Chevrolet Camaro

 

1999-2004 Chevrolet Silverado

 

2000-2004 Chevrolet Suburban, Tahoe

 

2002-2004 Chevrolet Avalanche

 

2003-2004 Chevrolet Express, TrailBlazer

 

1999-2004 GMC Sierra

 

2000-2004 GMC Yukon, Yukon XL

 

2001-2004 GMC Yukon Denali, Yukon XL Denali

 

2002-2004 GMC Sierra Denali

 

2003-2004 GMC Envoy XL

 

1998-2002 Pontiac Firebird

 

2004 Pontiac GTO

 

2003-2004 Hummer H2

 

with 4.8L, 5.3L, 5.7L or 6.0L V-8 Engine (VINs V, P, T, Z, G, S, N, U -- RPOs LR4, LM4, LM7, L59, LS1, LS6, LQ9, LQ4)

 

 

 

 

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A new spark plug has been released for use in the above vehicles. The new spark plug has an Iridium tip instead of the current Platinum tip. Due to the different tip design, the gap of the spark plug has also changed. The new spark plug, P/N 12571164 with AC Delco P/N 41-985, is gapped to 1.01mm (0.040 inches) when the spark plug is made. The spark plug gap is set during manufacturing and should not be changed or damage to the spark plug may result. Any new spark plug found to not be properly gapped should not be used.

 

 

 

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

 

 

© Copyright General Motors Corporation. All Rights Reserved.

 

 

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Document ID# 1396703

[timh975]

Hey all, thank you for the help.

[tobias]

This should help,

 

Document ID# 1396703

 

 

--------------------------------------------------------------------------------

 

 

Subject: Information on New Spark Plugs and Gapping #03-06-04-060 - (10/24/2003)

 

 

 

Models: 2004 Buick Ranier

 

2002-2004 Cadillac Escalade, Escalade EXT

 

2003-2004 Cadillac Escalade ESV

 

2004 Cadillac CTS-V

 

1997-2004 Chevrolet Corvette

 

1998-2002 Chevrolet Camaro

 

1999-2004 Chevrolet Silverado

 

2000-2004 Chevrolet Suburban, Tahoe

 

2002-2004 Chevrolet Avalanche

 

2003-2004 Chevrolet Express, TrailBlazer

 

1999-2004 GMC Sierra

 

2000-2004 GMC Yukon, Yukon XL

 

2001-2004 GMC Yukon Denali, Yukon XL Denali

 

2002-2004 GMC Sierra Denali

 

2003-2004 GMC Envoy XL

 

1998-2002 Pontiac Firebird

 

2004 Pontiac GTO

 

2003-2004 Hummer H2

 

with 4.8L, 5.3L, 5.7L or 6.0L V-8 Engine (VINs V, P, T, Z, G, S, N, U -- RPOs LR4, LM4, LM7, L59, LS1, LS6, LQ9, LQ4)

 

 

 

 

--------------------------------------------------------------------------------

 

A new spark plug has been released for use in the above vehicles. The new spark plug has an Iridium tip instead of the current Platinum tip. Due to the different tip design, the gap of the spark plug has also changed. The new spark plug, P/N 12571164 with AC Delco P/N 41-985, is gapped to 1.01mm (0.040 inches) when the spark plug is made. The spark plug gap is set during manufacturing and should not be changed or damage to the spark plug may result. Any new spark plug found to not be properly gapped should not be used.

 

 

 

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

 

 

© Copyright General Motors Corporation. All Rights Reserved.

 

 

--------------------------------------------------------------------------------

Document ID# 1396703

 

I love you, Rich.

[MS3DALE]

WTF!

 

Go pick on Jeff!!

[tobias]

WTF!

 

Go pick on Jeff!!

 

I was honestly wondering about this situation. I just put new 41-985's in the Tahoe last weekend and knew they were gapped at .040 but I also was looking through the manual last night and saw it calling for .060. Your post cleared everything up for me! Thanks!

[MS3DALE]

OK,I was gonna' say.....man this thread is over 3 years old,WTF!

 

BTW...Headin' down towards your Dad's tomorrow morning,hope the weathers nice down there this weekend!

[MS3DALE]

Oh BTW....The bulletin above has been updated to cover up to the 09's as well now.

[tobias]

OK,I was gonna' say.....man this thread is over 3 years old,WTF!

 

BTW...Headin' down towards your Dad's tomorrow morning,hope the weathers nice down there this weekend!

 

You are a travelin' machine!

[MS3DALE]

OK,I was gonna' say.....man this thread is over 3 years old,WTF!

 

BTW...Headin' down towards your Dad's tomorrow morning,hope the weathers nice down there this weekend!

 

You are a travelin' machine!

 

 

Yeah! Then I'm headin' back down next month for this.....Earnhardt car show

My buddies boss ask me if I'd help them out down there for it,Looks like a good time!

Oh...and I'll be back in Oct. for the NASCAR race too!!

[2COR517]

Regardless of the type of plug (iridium, platinum, etc) the gap should be .040". It's just "convenient" it coincides with a new plug type.

[tobias]

Regardless of the type of plug (iridium, platinum, etc) the gap should be .040". It's just "convenient" it coincides with a new plug type.

 

The manual calls for .060 and the TSB clearly states the Platinum plug uses the .060. Why is it you say it doesn't matter?

[2COR517]

The document Rich posted does not say to gap platinum plugs at .060".

 

GM had a drive-ability problem caused by the big gaps with the Vortecs in 96. Sloppy idle, pinging, etc. The solution was to tighten the gaps down. The large gaps put a tremendous load on the entire ignition system. They issued a document some time ago to tighten the gaps down to .040", long before iridium plugs came out. I don't have the actual document, but a friend of mine who is very much in the know shared this info with me. Apparently this info was distributed through GMs "Techline", not a formal TSB. Which is why it doesn't show up on AllData. If you recall, GM tried big gaps in the seventies, it didn't work then either.

 

The coating, whether it's copper, platinum, iridium, doesn't change the physics of sparking that gap under the extreme pressure of the combustion chamber.

 

You can run whatever gap you like, I have mine at .040. I will tell you from first hand experience that when I had the Bosch+4 in my truck, with their huge gaps, I thought my motor was toast. Sloppy idle, overheating, no power, non stop pinging. I put in the AC Delcos gapped at .040 and it felt like a brand new truck. I only changed the plugs and had that difference.